The Rev. Dr. Gil Rendle, a United Methodist minister and author of seven books, has traveled across the nation for years as a consultant to a variety of Protestant mainstream denominations, witnessing a fundamental shift in the religious and spiritual landscape.

The change hasn't been sudden, but it has been persistent, significant and worrisome to many pastors and their congregations faced with declining membership.

With surveys showing one-third of Americans under age 30 indicating no religious affiliation and mainline Protestants listed as below 50 percent in the population, Rendle, like many religious leaders, sees a paradigm shift in modern American religion and says the reasons for it are many and complex.

Those who share his concerns on the issue will be able to hear him at 7 p.m. Tuesday in a talk entitled "The Changing Religious/Spiritual Landscape" at Spirit on Tap in the Goodnites Lounge in Crowne Plaza Reading, Wyomissing.

Spirit on Tap is a monthly program organized by the United Church of Christ and is designed to stimulate dialogue around issues of faith and spirituality.

"I think we are no longer at a point where we can simply fix or improve things without recognizing the need for substantive change that goes very deep," said Rendle, 65, who lives with his wife, Lynne, in Lower Heidelberg Township.

Married for 44 years, the couple have two sons and six grandchildren.

"While this is a time of crisis and challenge, it also is a time of opportunity," he said.

Since 2007, Rendle has served as a senior consultant with The Texas Methodist Foundation in Austin, Texas, focusing particularly on issues of change and leadership in Protestant denominations.

Before that, Rendle was as a seminar leader and consultant with the Alban Institute for clergy in Herndon, Va., and served as senior pastor from 1980-86 at Central Park United Methodist Church, 138 S. Sixth St., and from 1972-80 at Ridge Avenue United Methodist Church, Philadelphia.

His most recent book is "Journey in the Wilderness: New Life for Mainline Churches."

"In my lifetime, there has been a significant generational shift from group values to the individual," Rendle said. "And that shift is driven by a lot of things, including advertising and the media, technologies, changes in behavior and personal experiences."

At the root of the religious change, especially for younger people, is a desire to have a worship and religious experience rather than a Sunday faith explanation that too often has become deadening for them, Rendle said.

"Young people aren't asking others, 'Would you go to worship with me?' but rather "Would you like to participate in a mission project with me?' " Rendle said.

A call to mission or social action is still strong among the young, but certainly in a less doctrinaire and more flexible religious structure than has existed in the past, according to Rendle.

"There is a tremendous amount of creativity going on out across the country, including the cafe ministries where I will be speaking, and that type of gathering would not have been heard of 10 years ago," he said. "But you also have the growth of mega-churches and small cell churches, all of them experimenting with establishing different types of faith communities."

And, perhaps, that quest for creating community and social connection is the common denominator that still helps to fuel the interest in religion or spirituality, he said.

"Maybe we need better conversations and better questions to answer," Rendle said. "What is the purpose of God or Christ in our lives? How do we form community? How do we live out our value systems in that search for community?"

Rendle believes people are still seeking engagement, intimacy, shared experiences and the ability to learn from one another in a flexible framework.

"It is clear that what many mainstream churches are doing now is not sustainable, and we no longer have the luxury of not doing something," he said. "I feel if people don't have a sense of the depth of change that is going on, they will exhaust themselves trying the same things over and over that just don't work.

"The question is, how do we take institutions not currently sustainable and make them vital?" he asked.

It is a complex challenge, but not necessarily a new one.

"Every time the Israelites came out of the wilderness," Rendle said, "they asked the questions: How will we now be with God? And how will we now be with one another?"